The Research And Implementation Of Image-guided Radiation Therapy Quality Assurance Procedure

Objective:Image-guided Radiation Therapy is key technology of precise radiotherapy, it can significantly improve the precision of radiotherapy. The deviation of verification images could cause serious dose deviation, so the quality assurance of image-guided radiation Therapy is very important for both hardware and processes. In order to use on-board imager safety and precision, we need to establish a strict and perfection QA procedure, and check the equipment with reasonable frequentness.Methods:According to OBI Customer Acceptance Procedure and TG-142, TG-74reports of AAPM for medical linear accelerator and medical image, by the use of QA tools such as Cube Phantom, Leeds Phantom, Catphan-504, Performing the QA procedure allows the overall performance ofOBI meet the acceptable clinical standards. QA procedure should include Safety and functionality of the system, Geometrical Accuracy and Image quality.Results:All Geometrical Accuracy QA results are within tolerance, the blade position accuracy is not stable and the results can be affected by human factors, the blade position needs to be calibrated every one or two months. The results of2D2D match are accurate in longitudinaland lateral directions, within1mm tolerance. The max deviation of2D2D match is2mm in vertical direction. For image quality, Standard dose head scanning technique is better than pelvis scanning technique in CT numbers linearity test and gets the best result in uniformity test (P<0.05). For spatial resolution, the results of three scanning techniques are superior to the baseline value, head scanning technique is better than pelvis scanning technique. For density resolution, the results of high quality head and pelvis scanning techniques have no significant difference (p=0.175), and superior to the results of standard-dose head scanning techniques (t=15.2、17.0,P<0.01).Conclusions:By testing the OBI according to QA procedures, we can get the results and analyze whether they could satisfy the clinical needs. For the tests which are instable, we could pay more attention to them in routine QA program and daily work. For the tests which are stable, we could improve the QA efficiency by checking them in reasonable frequency. For the tolerance of some tests such as spatial resolution and density resolution, we should establish baseline of the equipment in view of their characteristics.